I think it was done purposely by people who want to stir up the insurgency even more than they already are, so the US will be justified in keeping its military forces in Iraq indefinitely. Same as that little leak about the koran being abused in Guantanamo. Keep things in a perpetual state of chaos and violence, and we won't ever have to get our military out of there. Same thing with Afghanistan. Everything makes sense when you put all the puzzle pieces together where they belong.